Electron tube

Abstract

An envelope has a glass bulb body and a cylindrical glass bulb base. The glass bulb body includes an upper hemisphere and a lower hemisphere. The upper hemisphere is curved in a substantially spherical shape. The lower hemisphere is substantially curved in a spherical shape and connects the upper hemisphere and glass bulb base. A photocathode is formed on the inner surface of the glass bulb body. An avalanche photodiode is disposed on the glass bulb body side relative to an intersection between an imaginary extended curved surface of the lower hemisphere within the glass bulb base and an axis. When light enters the photocathode, electrons are emitted from the photocathode. The electrons are converged at the position above and in the vicinity of the APD by an electrical field in the electron tube, so that the electrons enter the APD in an efficient manner and are detected satisfactorily.

1. An electron tube comprising:
 an envelope formed with a photo cathode in a predetermined part of an internal surface thereof, the envelope comprising:
 a cylindrical base; and 
 a main body having a first main body and a second main body that connects the first main body and the base, the main body having substantially a spherical shape; 
 
 an electron-bombarded semiconductor device provided on the main body side relative to an intersection between an axis of the cylindrical base and an imaginary-extended-curved-surface of the second main body that is located inside the cylindrical base; and 
 a supporting member that faces photocathode and supports the electron-bombarded semiconductor device, at least part of the supporting member being provided on a main body side relative to the intersection, the supporting member being conductive, and 
 an insulating tube that has one end and another end, the another end being connected to the envelope and the one end protruding inside the envelope, the supporting member being disposed on the one end of the insulating tube, the insulating tube being located on the cylindrical base side with respect to the imaginary-extended-curved-surface, 
 the semiconductor device detecting photoelectrons emitted from the photocathode in response to an incident light thereon, 
 wherein the supporting member comprises:
 a conductive portion; and 
 an inner stem connected to the one end of the insulating tube via the conductive portion, 
 wherein the electron tube further comprises a conductive member provided on the one end of the insulating tube and protruding outside the insulating tube to reduce the field intensity in the vicinity of the one end of the insulating tube, and 
 wherein the semiconductor device is disposed on the inner stem. 
 
 
   
   
     2. The electron tube as claimed in  claim 1 , further comprising:
 another conductive member provided on the another end of the insulating tube and protruding outside the insulating tube to reduce the field intensity in the vicinity of the another end of the insulating tube, 
 wherein the envelope further comprises an outer stem connected to the another end of the insulating tube, at least a part of the outer stem that is connected to the another end of the insulating tube being conductive. 
 
   
   
     3. The electron tube as claimed in  claim 2 ,
 wherein the envelope is applied with a ground potential, and 
 wherein the semiconductor device is applied with a positive potential. 
 
   
   
     4. The electron tube as claimed in  claim 1 ,
 wherein the envelope is applied with a ground potential, and 
 wherein the semiconductor device is applied with a positive potential. 
 
   
   
     5. The electron tube as claimed in  claim 1 , wherein the insulating tube is provided on the cylindrical base side relative to the intersection. 
   
   
     6. The electron tube as claimed in  claim 5 , wherein the electron-bombarded semiconductor device is disposed on a downstream side of the supporting member with respect to a direction from the cylindrical base to the main body along the axis of the cylindrical base. 
   
   
     7. An electron tube comprising:
 an envelope formed with a photocathode in a predetermined part of an internal surface thereof, the envelope comprising:
 a cylindrical base; and 
 a main body having a first main body and a second main body that connects the first main body and the base, the main body having substantially a spherical shape; 
 
 an electron-bombarded semiconductor device provided on the main body side relative to an intersection between an axis of the cylindrical base and an imaginary-extended-curved-surface of the second main body that is located inside the cylindrical base; and 
 a supporting member that faces photocathode and supports the electron-bombarded semiconductor device, at least part of the supporting member being provided on a main body side relative to the intersection, the supporting member being conductive, and 
 an insulating tube that has one end and another end, the another end being connected to the envelope and the one end protruding inside the envelope, the supporting member being disposed on the one end of the insulating tube, the insulating tube being located outside the main body; 
 the semiconductor device detecting photoelectrons emitted from the photocathode in response to an incident light thereon, 
 wherein the supporting member comprises:
 a conductive portion; and 
 an inner stem connected to the one end of the insulating tube via the conductive portion, 
 wherein the electron tube further comprises a conductive member provided on the one end of the insulating tube and protruding outside the insulating tube to reduce the field intensity in the vicinity of the one end of the insulating tube, and 
 wherein the semiconductor device is disposed on the inner stem. 
 
 
   
   
     8. The electron tube as claimed in  claim 7 , further comprising:
 another conductive member provided on the another end of the insulating tube and protruding outside the insulating tube to reduce the field intensity in the vicinity of the another end of the insulating tube, 
 wherein the envelope further comprises an outer stem connected to the another end of the insulating tube, at least a part of the outer stem that is connected to the another end of the insulating tube being conductive. 
 
   
   
     9. The electron tube as claimed in  claim 8 ,
 wherein the envelope is applied with a ground potential, and 
 wherein the semiconductor device is applied with a positive potential. 
 
   
   
     10. The electron tube as claimed in  claim 7 ,
 wherein the envelope is applied with a ground potential, and 
 wherein the semiconductor device is applied with a positive potential. 
 
   
   
     11. The electron tube as claimed in  claim 7 , wherein the insulating tube is provided on the cylindrical base side relative to the intersection. 
   
   
     12. The electron tube as claimed in  claim 11 , wherein the electron-bombarded semiconductor device is disposed on a downstream side of the supporting member with respect to a direction from the cylindrical base to the main body along the axis of the cylindrical base.